The commented code below can help you:

const animals = ["cat", "dog", "reindeer", "penguin", "crocodile"]
const vowels = ['a', 'e', 'i', 'o', 'u']

animals.forEach(animal=>{
  let counter=0
  //spliting the word in letters
  animal.split('').forEach(letter=>{
    //checking if the letter is really a letter and if it is not a vowel
    if(letter.toLocaleLowerCase()>='a'&&letter.toLocaleLowerCase()<='z'&&!vowels.some(v=>v===letter.toLocaleLowerCase()))
    counter++
  })
  if(counter>=4)
  console.log(animal)
})

With String match() method for pattern-matching, and Array.prototype.filter() for conditional screening of items, we can write a concise one-liner:

> const animals = ["cat", "dog", "reindeer", "penguin", "crocodile"]

> animals.filter( animal => animal.match(/[^aeiou]/gi).length >= 4)
["reindeer", "penguin", "crocodile"]

Do study regex as much as possible. Here are few resources: quick overview, deatiled demo